There are many types of thermal containers from the common foam-type picnic coolers to sophisticated insulated containers with hermetically sealed covers. When hot materials are placed in such a container, moisture in the form of steam may be given off creating a high humidity environment within the container. If hot food is to be transported in such a thermal container, the steam emitted may cause the food to become soggy or to become otherwise undesirable. A cold material placed in an insulated container may "sweat" causing the materials contained therein and the interior surfaces of the container to become moist and may also alter the characteristics of the materials.
Caggiano, in U.S. Pat. No. 4,861,632, teaches a laminated packaging material that can be use to formulate containers for storing or transporting a variety of products. Sheets of this material can be combined to form bag-type containers. The outer layer of the material is water impervious, the middle layer is a water absorbent substance such as sheets of paper toweling, and the inner layer is water impervious with perforations. Another embodiment of the invention uses paper toweling impregnated with a desiccant as the middle layer and a further embodiment includes a layer of granulated desiccant between layers of paper toweling. The material is designed to absorb any moisture given off by the products placed in the container. These containers are flexible and are not practical for transporting hot or cold foods or other substances which must be kept in rigid containers to maintain their integrity.
Beaver, Jr. et al, in U.S. Pat. No. 5,372,429, teaches a shipping pouch that is made up of three layers. An outer bag contains a filler layer in the form of a compressible absorbent material capable of conforming to the shape of any object that may be placed in an inner bag. Cushioning and absorbent materials such as cellulose, sawdust or wool are suggested as well as several desiccants. This pouch is designed to accommodate irregularly shaped objects that can be broken or otherwise damaged during shipping and is not practical for transporting foods. The pouch is not designed to maintain the temperature fits contents.
The invention of Cullen, U.S. Pat. No. 5,148,613, teaches a covered container used to absorb water from the environment of a closet. The rigid container has a perforated elastic diaphragm suspended from the inside of the cover which holds a quantity of a deliquescent material. There is an opening in the cover over which is stretched a membrane which permits water vapor, but not liquid water to enter the container. The water vapor enters the container through the membrane and is absorbed into the deliquescent material until the solution formed therefrom drips down into the container. As the deliquescent material is used up the elastic diaphragm contracts so as to prevent the solution in the container from making contact with the diaphragm. This container is not geared to contain foods or other materials. It is designed only to remove water from its external environment.
A cosmetic case having a removable refrigerant pack is taught by Abtahi in U.S. Pat. No. 4,892,226. The side walls of the interior of the case are covered with two layers of an material such as foam or a sponge-like material and the frozen pack is placed between these layers so that any condensation that may form on the pack is absorbed and the cosmetics are maintained in a substantially dry condition. The refrigerant pack can be frozen by placement in the freezer compartment of the refrigerator. As the foam absorbs the condensation it becomes wet and the environment within the container remains at a high humidity. This type of container is not useful when the interior of a container is desired to be maintained at low humidity.
Futagawa, in U.S. Pat. No. 5,706,937, teaches a dual pouch for carrying medical mixtures. The upper pouch is designed to contain a dry substance and the lower pouch contains the liquid. A seal between the two pouches is broken when the two substances are to be mixed. The upper pouch has laminated walls which contain a layer of water absorbent material such as a film coated with silica gel on one side and a film containing the inorganic filler DRY-KEEP on the other side. The laminate is designed to intercept moisture and oxygen. This container is flexible, sealed, and prevents moisture from entering the interior. It cannot be readily opened and closed or used to contain a substance that may give off moisture from within the pouch.
Though the prior art describes a variety of containers, none is designed to transport materials that must be maintained at high or low temperatures while at the same time preventing the increase in humidity within the container. Such moisture within a transport container can damage foods and medical supplies. If the container is vented to provide an outlet for the moisture, the temperature cannot be maintained at the desired level. There is a need for a container that can be used to transport hot foods while preventing the food from becoming soggy or otherwise unappetizing. There is also a need for a container that can also be used to keep foods and other materials cold without having condensation dampening the interior of the container to the detriment of its contents.